Preparation of thiol esters

ABSTRACT

THIOL ESTERS OF THIOLCARBOXYLIC ACIDS AND THIOLPHOSPHORIC ACIDS ARE PREPARED BY REACTING THE ACIDS WITH A VINYLIC HALIDE. THE REACTION IS CONDUCTED IN THE LIQUID PHASE IN THE PRESENCE OF A FREE RADICAL INITIATOR. THE FREE RADICAL ADDITION REACTION FOR THE FORMATION OF THE THIOL ESTERS IS CONDUCTED AT MODERATE TEMPERATURES AND MODERATELY ELEVATED PRESSURES. THE PRODUCTS FROM THE REACTION, IN PARTICULAR THE ESTERS OF THIOPHOSPHORIC ACIDS, ARE HIGHLY EFFECTIVE NEMATOCIDES.

United States PatentOfice P 3,687,830 Patented Aug. 29, 1972 3,687,830PREPARATION OF THIOL ESTERS Alexis A. Oswald, Mountainside, and WolfgangH. Mueller, Elizabeth, N..I., assignors to Esso Research and EngineeringCompany No Drawing. Continuation-impart of application Ser. No. 3576,504, Aug. 26, 1966. This application Nov. 20, 1968, Ser. No. 777,500v Int. Cl. B01; 1/10; C07c 153/07; C07f 9/02 US. Cl. 204-158 R" 10Claims ABSTRACT OF THE DISCLOSURE Thiol esters of thiolcarboxylic acidsand thiolphosphoric acids'are prepared by reacting the acids with avinylic halide. The reaction is conducted in the liquid phase in thepresence of. a free radical initiator. The free radical additionreaction for the formationof the thiol esters is conducted at moderatetemperatures and moderately elevated pressures. .The products from thereaction; in particular the esters of thiophosphoric acids, are highlyelfective nematocides I acids. More particularly, the invention relatesto the formation of the thiol esters through theliquid phase reaction ofthiolcarboxylic and thiolphosphoric acids with vinylic halide compounds.Additionally, th e invention per} tains to a process forvthe formationof 2-substituted thioalkyl thiophosphates by reacting the thiol esterswith a metal mercaptide or thiolate compound.

(II) Descriptionof the prior art The existence of estersofthiolcarboxylic and thiol phosphoric acids have been reported in theliterature. As

is. disclosed in US. 2,611,728 and Canadian Pat 510,162, u

the usual manner of forming compounds of this general type involves theuse of substitution, reaction. In; US. 2,61l,728,-it.is reported thatthe subject compounds could be formed by reacting ammonium diethyldithiophosphate with ethylene dichloride in a refluxing acetonesolution. With this reaction, a beta-chloroethyl diethyl dithiophosphateproduct was produced as well as ammonium chloride by-products. In thisreaction, however, some ethylene bis-diethyldithiophosphate is alsoformed as a by-product in accordance with the following equation: I

ClCHzCHzCl (C2Hs )2 SzNH4 (0211 0)? SCHzCFlzCl SUMMARY OF THE INVENTIONIt has now been discovered that thiol esters can readily be produced bythe addition reaction of certain thiol acids with vinylic halides. Withthis reaction undesirable by-products can be avoided. The: thiol estersproduced with the present process can be employed as nematocides orreacted further with metal mercaptide or The thiol esters of thisinvention are easily prepared by reacting a thiol acid with a vinylichalide in the liquid phase in the presence of a free radical initiator.The thiol acids used in accordance with thisinvention arethiolcarboxylic acids and the thiolphosphoric acids having the followinggeneral formulae respectively:

wherein R is selected from the group consisting of monovalent C to Calkyl radicals, monovalent C to C aryl radicals and substitutedderivatives thereof. Preferably R-is a C to C alkyl radical or a C toC16 aryl radical. Desirably, Y is a sulfur or oxygenatom, preferably asulfur atom. Most preferably R is a monovalent C to C alkyl radical. Itis preferred that the alkyl and arylv groups be unsubstituted; howeverhalogen, e.g. chloro; alkylthio; alkoxy; aryl; etc. substituent groupsmay be added to the basic alkyl and aryl radicals withoutdiminishing theactivity of the product.

' Representative examples of useful thiol acids include thiolaceticacid, thiolstearic acid, thiooctanoic acid, thiobenzoic acid, diethyldithiophosphoric acid, dimethyl dithiophosphoric acid, dilauryldithiophosphoric acid, dioctadecyl dithiophosphoric acid, diphenyldithiophosphoric acid, ditolyl dithiophosphoric acid, ethyl phenyldithiophosphoric acid, etc.

As stated earlier, the thiol esters are prepared by reacting either ofthe aforementioned thiol acids with a vinylic halide. The vinylichalide, particularly vinyl chloride, reacts :quickly and easily in theliquid phase in the presenceof a free radical catalyst with either ofthe aforementioned thiol acids. It was surprisingly discovered thatZ-haloalkenes, particularly 2-halopropenes also react easily and quicklywith the thiol acids. This is surprising in view of the fact that thehigher l-haloalkenes react very slowly to produce a very small yield.

Thus, the vinylic halides suitable for the practice of this inventionhave the following formula:

wherein is a halogen atom, preferably a chlorine, bromine or fluorineatom, most preferably a chlorine atom, and R" is either a hydrogenradical or a monovalent substituted or unsubstituted C to C alkyl group.Preferably, R" is either a hydrogen radical or a C -C alkyl I radical.:It is preferred that the alkyl groups be unsubstituted; however,certain substituent groups such as chloro, alkylthio, alkoxy, aryl,etc., can be added to the alkyl groups. In the ordinary production of2-haloalkenes having at least three carbon atoms, the corresponding 1-haloalkene isomers are also produced.- In accordance P include vinylbromide, propenyl chloride, butenyl chlothe production of thiolatecompounds for the production of systemic insecticides.

ride, octadecenyl chloride, phenylpropenyl chloride, methylthio vinylchloride, hexenyl bromide, vinyl fluoride, vinylidene chloride,fluorovinyl chloride, etc.

The reactions of thiolcarboxylic acids and thiolphosphoric acids withvinylic halides are illustrated by the following equations:

P SH H1C=C-R P-S-CHz-([JH-A no ii R X wherein X, Y, R, R" are aspreviously described. -In each of the reactions, the mole ratio of thiolacid to vinylic halide should be maintained in the. range of from 1:15to 3:1 and preferably in the range of 1:1.1 to 2:1. The reaction isusually carried out in the absence of any solvent; however, it may benecessary to use a solvent where a non-viscous reaction medium isdesired. Aliphatic hydrocarbons, ketones and ethers, particularlythioethers, are the preferred solvents. Materials such as n-heptane,cyclohexane, diethyl ether, dimethyl sulfide, methylethyl ketone, etc.can be readily employed. T

The reaction may be initiated with the use of a free radical initiator,such as radiation, e.g. ultraviolet light, heat, gamma rays, etc. orwith a chemical initiator such as peroxides or azo compounds, e.g.dicumylperoxide, azo-bisisobutyronitrile, etc. If a chemical initiator'is used, it should usually be present in the rangeof 0.1 to 5 wt.percent preferably in the range of 0.1 to 3 wt; percent based onstarting reactants.

The reaction can be completed within a range of from 0.1 hour to 3 daysat ambient temperature. Thereaction should be maintained at atemperature of from 150 C. to +150 C., preferably from --80 to 100 C.The pressure within the reaction zone should be maintained at levelssuflicient to assure a liquid phase reaction system. Reaction zonepressure may vary within the range of from 1 to 150 atmospheres andpreferably from 1 to 80 atmospheres.

The compounds produced with the present process are eifectivenematocides. In addition, they can beemployed as starting materials inthe synthesis of commercial, systemic insecticides such as Systox andDisyston and, in general, for the synthesis of 2-substituted thioalkylthiophosphates. Such materials are produced according to the followingreaction sequence:

PS-CH2CHR" MSR' Ito i I PSOHz-CH-SR' MX R0 Y wherein MSR' represents ametal mercaptide or thiolate compound such that M designates amonovalent moiety such as sodium, ammonium, or potassium radicals and Ris a hydrocarbyl radical such as a C -C alkyl radical or a C -C acylradical such as an acetyl or benzoyl radical.

The above reaction is carried out in the liquid phase at temperaturesranging from -10 to 150 C., preferably 10 to 100 C. The reaction may beconducted in the presence of typical aliphatic and aromatic hydrocarbondiluents. Reaction pressure is not critical; however, liquid phaseconditions should be maintained.

The following examples demonstrate the process of the invention and theeflicacy of the compounds prepared according to the process of thisinvention. I

EXAMPLE 1 A stirred mixture of 38 grams (0.5 mole) of thiolacetic acidand 38 grams (0.5 mole) of 2-chloropropene was irradiated in a quartztube with a 70 watt high pres: sure immersion ultraviolet lamp for sixhours at 17 C. A nuclear magnetic resonance spectrum of the. mixtureindicated that 70% of the vinylic hydrogens disappeared due to theformation of 1-acetylmercapto-2-chloropropane. The pure product wasisolated by fractionation in vacuo as a liquid boiling between 28-29 C.at 0.1 mm. of mercury pressure and the yield was 39 grams whichAnalysis. Calculated for C HQCIO S (percent): C 39.60; H, 5.32; Cl,23.38; S, 21.15. Found (percent): C, 39.45; H, 5.68; C], 23.10; 5,21.40.

EXAMPLE 2 A stirred mixture of 47.4 grams (0.3 mole) of 90% technical,grade dimethyldithiophosphoric acid and; 22 grams (0.3 mole) of isomericchloropropenes (1- and 2- in a 3 to 1 ratio) was reacted in a'quartztube under the influence of ultraviolet radiation at 15 C. for 65 hours.A subsequent analysis of the mixture byspectroscopy indicated thatalmost all of the 2-chloropropene but none of the l-chloropropenereacted. The crude product was taken up in 300 milliliters of ether andthe unchanged dimethyldithiophosphoric acid was removed by washing thesolution with 5% sodium hydrogen carbonate. The ethereal phase was thenseparated, dried and fractionally distilled. A colorless liquid boilingat 77-79" C. at 0.1 mm. of mercury pressure, 18.3 grams of purel-dimethylthiophosphorylmercapto 2 -chloropropane was thus obtained. 1

Analysis.Calculated for C H O ClPS (percent): C, 25.59; H, 5.15; P,13.19; S, 27.33. Found (percent): C, 25.82; H,"5.25; P, 12.98; S, 27.77

EXAMPLE 3 A stirred mixture of 63.5 grams of dimethyldithiophosphoricacid and 34.2 grams of vinyl chloride was irradiated in a sealed quartztube with a 70 watt high pressure immersion ultraviolet lamp for 48hours at 17 C. The reaction mixture was then dissolved in 200milliliters of ether and washed with 5% aqueous sodium bicarbonate. Theethereal solution was dried over magnesium sulfate and the ether removedat reduced pressure. The crude product weighed 76.44 grams and proved tobe 85% pure on gas-liquid chromatography analysis. Fractionaldistillation yielded 57 grams (65% yield) of Z-chloroethyldimet'hyldithiophosphate.

Analysis-Calculated for C H PS O Cl (percent): C, 21.77; H, 4.53; P,14.06; S, 29.02; Cl, 16.10. Found (percent): C, 21.85; H, 4.69; P,14.00; S, 29.63; Cl, 15.97.

Similar additions could be carried out under initiation by gammaradiation originating from a 4500 Curie Co source placed at about 6centimeters distance from the reaction mixture.

EXAMPLE 4 EXAMPLE 5 2-chloroethyl dimethylmonothiophosphate can be.prepared in a similar manner by the additionof dimethylthiophosphoricacid to vinyl chloride. 1 I 1 EXAMPLE 6 The 2-haloethyl thiolesters,synthesized as described in Examples 1-5, were tested as nematocides.The nematocidal tests were carried out by the so-called modified methodof the Wisconsin Alumni Research Foundation using tomato plants pottedin soil interested with an unknown strain of parasitic root knotnematode. Evaluation of the effectiveness of the compound was made onthe basis of the signs of nematode activity, i.e. root knots formed,after about six weeks. On the basis of the number of root knots formedper plant, readings of nematode control were made and calculated inpercent. They are shown per 4 inch acre rate, chloroalkyl esters ofthiolacetic' acid TABLE I I Nematocidal Efie'cttveness of 2- Haloa1kylThiolesters Active ingredient Percent control of root knot nematodes atsuch surface. active agents are. advantageously employed in'both thesolid and liquid compositions. The agents can be anionic, cationic, or.nonionic in character. Typical classes of surface active agents includealkyl sulphonates, alkyl aryl sulphonates, alkyl sulfates', fattyacidesters of polyhydriealcohols andthe like.

- various application rates e 40 20 .10 6 Example Structure lbs/acrelbs/acre lbs/acre lbs/acre l CHSCOSCHZCHCI 99 70 8 CH8 I Y I i l 2(CH3O)zPS OH CHOl 92 5s o S CH:

3 (CHgOhfi S CHgCHzCl 99 95 87 4 (CzHsOhfiSCHgCHzCl 0 O 5 (CHsOhfi SCHzCHzCl Number of plants surviving N0 treat- Soil Example 1 Example 4ment Inoculated 8 0 Uninoouiated 14 12 The results show that a highernumber of plants survived in both the inoculated and uninoculated soilsif they were treated with the adduct of Example 1 or Example 4.

The thiolesters produced with the present process may vary from highlymobile liquids to solids and, while they may be applied as such to thesoil habitat of the nomatodes, it has been found desirable to apply themin a carrier. Suitable carriers include inert solids for the formationof dust or, more preferably the nematocide is suspended in a suitableliquid diluent, preferably water. There can also be added surface activeagents and inert solids in such liquid formulations. From 0.05 to 1 wt.percent of a surface active agent may be employed. The active ingredientshould be employed in a concentration of from 0.011 to 95 wt. percent ofthe entire composition.

In place of water, there can be employed organic solvents as carriers,for example, hydrocarbons, such as benzene, toluene, xylene, kerosene,diesel oil, fuel oil, and petroleum naphtha; ketones, such as acetone,methylethyl ketone, and cyclohexanone; chlorinated hydrocarbons, such ascarbon tetrachloride, chloroform, trichloroethylene, andperchloroethylene; esters, such as ethylacetate, amylacetate and butylacetate, glycol ethers, for example, monomethylether of ethylene glycoland monomethylether of diethylene glycol, alcohols, for example,ethanol, isopropanol, and amyl alcohol.

The thiolesters can also be applied along with inert solid fungicidaladjuvants or carriers, such as talc, pyrophyllite, synthetic finesilica, kieselguhr, chalk, diatomaceous earth, lime, calcium carbonate,bentonite, fullers earth, cotton seed balls, wheat flour, soy beanflour, etc.

It is frequently desirable to incorporate a surface active agent in thenematocidal compositions of this invention.

The invention has been described with a certain degree of particularity.It is to be understood that the invention is not limited to the specificexamples which have been offered merely as illustration since othermaterials can be prepared and that modifications may be made withoutdeparting from the spirit of the invention.

What is claimed is:

1. A process for; the production of 2Fha1oalkylthiol esters comprisingreacting in the liquid phase in the presence of a free radical initiatora thiol acid of the formula wherein R is selected from the groupconsisting of C to C alkyl radicals, C to C aryl radicals andsubstituted derivatives thereof, with a vinylic halide of the formula HO=('J RII R0 R-C-SH I: A and P---SH ll R0 8 wherein R is selected fromthe group consisting of C to C alkyl radicals and C to C aryl radicals,with a vinylic halide of the formula:

wherein R" is selected from the group consisting of hydrogen and C to Calkyl radicals and X is a halogen atom selected from the groupconsisting of chlorine, bromine, and fluorine atoms, said reaction beingconducted in the liquid phase in the presence of a free radicalinitiator at a temperature varying from to C.

3. The process of claim 2 wherein R" is a C to C alkyl radical and saidvinylic halide is present in admixture with a l-haloalkene.

4. The process of claim 2 wherein said free radical initiator isradiation.

thiophosphates comprising reacting a dithiophosphoric acid of theformula: 1

P-SH Ro wherein R is selected from the group consisting of methyl andethyl radicals, with a 2-chloropropene in admixture with l-chloropropenein the liquid phase in the presence of an ultraviolet radiation source,at a temperature varying-from -80 tolOO C. g I i a 10. The process ofclaim 9 wherein said 2-chl'oropropene is reacted to a' substantiallycomplete conversion;

' References Cited- UNITED STATES PATENTS 2,810,687 10/1957 'Rueggeberget al 204-158 3,318,940 5/1967 ;Laddr. i 204158 3,441,589 4/1969 Oswaldl 204158 3,483,278

12/1969 Mueller et ,al. i. 204,-158

How n s. WILLIAMS, Primary Examiner U.S. 01. xii. 204-158 HE; 260-455 R,979

